This paper deepens the empirical analysis of peer networks by considering simultaneously their eff ects smoking participation and smoking intensity. Peer network is key in determining the smoking behaviour of youths, but the magnitude of the e ffects is still debated, questioned and inconclusive. I used a control function approach, a two-step least square and the fixed e ffect method to address the potential endogeneity of peer network. The results suggest positive and signi cant peer e ffects on smoking participation and intensity. While the magnitude of the estimates of smoking participation varies across methodological approaches (ranging between 4 and 20 percent), that of smoking intensity ranges between 3 and 22 percent. Including older adults in the peer reference group increases the peer e ects. The findings suggest that policies (excise tax) that directly a ect the decision to smoke and the smoking intensity of the peer reference group are likely to a ect own smoking behaviour.